A start electric motor is mounted even on a small internal combustion engine such as a portable working machine to facilitate a starting operation. The present applicants have previously filed a Japanese patent application, Ser. No. 166473/1988, which discloses an apparatus wherein an ambient temperature is detected by a temperature switch in order to supply a rich mixture to the engine at the time of cold start, and when the ambient temperature is low, an electric fuel pump is driven to supply start fuel to an air intake passage of a carburetor. However, it is preferable that the addition of the electric fuel pump and the temperature switch be avoided, since these increase the cost and the apparatus becomes larger in size with a weight increase.
In view of the aforementioned problems, an object of the present invention is to provide an apparatus for supplying start fuel for a carburetor which is low in cost and small and light weight wherein start fuel is automatically supplied to a carburetor in correspondence to the starting conditions of the engine without using a temperature switch.
For achieving the aforesaid object, the present invention provides an arrangement, in an internal combustion engine, which is provided with a fly-wheel magneto for supplying start fuel from a fuel chamber of a carburetor to an air intake passage via an electromagnetic valve. The electromagnetic valve is actuated by an output signal of a primary coil of the fly-wheel magneto.